Low crosstalk heterogeneous sixteen-core four-mode fiber with concave-convex double-type refractive index profiles.

Multi-core few-mode fiber based on space division multiplexing technology is widely regarded as the primary solution to the optical communication capacity issue. However, the quality of the communication signal of the multi-core few-mode fiber depends on the degree of energy coupling between the cores. Thus, we propose a heterogeneous sixteen-core four-mode fiber that achieves low inter-core crosstalk, which first employs a combination of concave and convex double-type refractive index profiles. The advantage of this double-type refractive index profile is that the fiber can more conveniently regulate the phase differences of the same modes in adjacent cores. At the wavelength of 1550 nm and the optimal fiber parameters, all cores of the proposed fiber support four LP modes, and the inter-core crosstalk of all LP modes is less than -72 dB/km. This research demonstrates the efficacy of the proposed fiber in enhancing signal quality and presents innovative ideas and solutions for the future design of various low crosstalk multi-core few-mode fiber.